Low-dose benzo[a]pyrene exposure induces hepatic lipid deposition through LCMT1/PP2Ac-mediated autophagy inhibition.

Non-alcoholic fatty liver disease (NAFLD) is a progressive disorder of liver metabolism and has become the most common chronic liver disease worldwide. Benzo[a]pyrene (BaP) is recognized as a potent carcinogen, but the effect of low-dose BaP on the development of NAFLD has not been well-studied, and its molecular mechanism is still unknown. In this study, we demonstrated that low-dose BaP induced hepatic steatosis in a mouse model with a notable increase in hepatic lipid content. Interestingly, mRNA expression of genes related to fatty acids uptake or synthesis was not significantly altered after BaP exposure. Instead, we found that low-dose BaP promoted lipid deposition in primary mouse hepatocytes by inhibiting autophagy, which was regulated through Leucine carboxyl methyltransferase-1 (LCMT1) mediated Protein Phosphatases 2A subunit C (PP2Ac) methylation. The role of LCMT1 in BaP-induced steatosis was further validated in a liver-specific lcmt1 knockout (L-LCMT1 KO) mouse model. In this study, we provided evidence to support a novel mechanism by which BaP induces the development of hepatic steatosis through PP2Ac mediated autophagy inhibition. These findings provided new insight into the pathogenesis of NAFLD induced by environmental exposure to low-dose BaP.

Regulation PP2Ac methylation ameliorating autophagy dysfunction caused by Mn is associated with mTORC1/ULK1 pathway.

Manganese (Mn) exposure leads to autophagy dysfunction and causes neurodegenerative diseases such as Parkinson's syndrome and Alzheimer's disease. However, the mechanism of neurotoxicity of Mn has been less clear. The methylation of the protein phosphatase 2A catalytic subunit determines the dephosphorylation activity of protein phosphatase and plays an important role in autophagy regulation. In this investigation, we established a model of Mn (0-2000 µmol/L) exposure to N2a cells for 12 h, used the PPME-1 inhibitor ABL-127, and constructed an LCMT1-overexpressing N2a cell line. We also regulated the PP2Ac methylation level and explored the effect of PP2Ac methylation on Mn-induced (0-1000 µmol/L) N2a cellular autophagy. Our results showed that Mn > 500 µmol/L induced N2a cell damage and increased oxidative stress. Moreover, Mn modulated autophagy in N2a cells by downregulating PP2Ac methylation, which regulated mTORC1 signaling pathway activation. Both ABL-127 and LCMT1 overexpression can upregulate PP2Ac methylation in parallel with ameliorating N2a cell abnormal autophagy induced by Mn, Briefly, the upregulation of PP2Ac methylation can ameliorate the autophagy disorder of N2a by Mn and effectively alleviate Mn-induced cytotoxicity and oxidative stress, indicating that regulation of autophagy is a protective strategy against Mn-induced neurotoxicity.

Systemic toxicity evaluation of novel tobacco products in Caenorhabditis elegans.

Under strictly Framework Convention on Tobacco Control, novel tobacco products are going to be promising alterations to consumers and manufactures. Even though the novel tobacco products have been considered less harmful than traditional tobaccos, there is a few knowledges about the subsequent substances during consume and their impacts to the consumers due to short introduction into the market. Thus, the present study aims to investigate the adverse effects of novel tobacco products on Caenorhabditis elegans(C. elegans) and to provide relevant references for novel tobacco products toxicity research and assessment. C. elegans individuals at L4 stage were exposed to different kinds of novel tobacco products, including electronic cigarettes liquid (e-liquid), the extract of e-cig aerosol (e-aerosol), mint and black tea flavor snus. After specific exposure time, the multiple toxic endpoints of C. elegans were measured, including acute toxicity, locomotion behavior, body length, and life-span. The oxidative stress was tested too. According to acute toxicity assays, the half lethal dose of four novel tobacco products calculated from theoretical nicotine concentration, ranked as follows e-liquid (0.29 mg/ml) > the extract of e-cig aerosol (0.43 mg/ml) > mint flavor snus (1.20 mg/ml) > black tea flavor snus (1.50 mg/ml). The equivalent lethal rate 5%~20% of four novel tobacco products were applied to following experiments. These novel tobacco products damaged nematode's locomotion including head thrashing and body bending, the damage was most evident in two flavors of snus. The similar trends were found in reproductive performance investigation. At tested concentrations, the retardation development of C. elegans was found throughout all stages with peak blockage at adulthood. Life-span tests showed that novel tobacco products at 5% lethal rate seemed no significant effect on affected the life-span of nematodes, with snus shortened the lifespan of C. elegans at 20% lethal rate. Imaging stress response indicted four types of tobacco productions causing stress response in C. elegans. Exposed to either 5% or 20% lethal levels (5% and 20%), the percentages of worms with DAF-16 redistribution among all groups varied, with higher frequencies in both snus. Summary, novel tobacco products caused multiple adverse impacts to C. elegans, including acute toxicity, locomotion behavior disruption, brood size reduction, development retardation, and life-span reduction. The toxicity was associated with both the feature and concentration of tobacco products, and oxidative stress was the main mechanism.